The disclosure relates to an exposure apparatus, and more particularly to an exposure apparatus for manufacturing a semiconductor device.
In a semiconductor manufacturing process, a photolithography process for transferring a pattern onto a plane substrate using light has been known. In the photolithography process, a pattern formed on a photomask is transferred (exposed) to a photosensitive layer (photoresist) applied on a wafer by an exposure apparatus. As the exposure apparatus, a batch exposure-type projection exposure apparatus such as a stepper or a scanning exposure-type projection exposure apparatus such as a scanner is used.
Along with the recent improvement of a fine processing technique, a technique for increasing the resolution has been required for these exposure apparatuses. As a technique for increasing the resolution of the exposure apparatus, shortening the wavelength of an exposure light source or increasing the numerical aperture of a projection optical system has been known. However, the depth of focus of the projection optical system becomes smaller in inverse proportion to the square of the numerical aperture, and becomes smaller in proportion to the wavelength. Accordingly, a technique (technique for reducing k1) to increase the resolution without depending on these parameters has been required. As the technique for reducing k1, an irregular illumination method and a phase shift mask method have been known in the illumination field and the mask field, respectively.
Regarding the irregular illumination method to increase the resolution, Japanese Unexamined Patent Application Publication No. 2006-278979 discloses an exposure apparatus that uses one-row quadrupole illumination whose light quantity is increased by four secondary light sources arranged along a straight line parallel to the X-axis in a pupil surface of an illumination optical system when one-direction dense patterns aligned at predetermined pitches in the X-direction are exposed, and changes the polarization state of illumination light to linear polarization in the direction orthogonal to the X-axis using two outer secondary light sources and to linear polarization in the direction parallel to the X-axis using two inner secondary light sources (see “ABSTRACT”).
Further, Japanese Unexamined Patent Application Publication No. 2010-093291 discloses an exposure apparatus that includes illumination pupil forming means to form, on or near a pupil surface of an illumination optical apparatus, illumination pupil distribution having light intensity distribution located at a central region including the optical axis and light intensity distribution located at a plurality of peripheral regions apart from the optical axis, and region changing means to change the position and size of the light intensity distribution located at the peripheral regions independently from the light intensity distribution located at the central region (see “ABSTRACT”).